Bonobos help strangers without being asked

November 7, 2017 by Robin A. Smith, Duke University
Close primate cousins with whom we share 99 percent of our DNA, bonobos will help strangers even when there is no immediate payback, and without having to be asked first. Credit: Lola ya Bonobo Sanctuary.

A passer-by drops something and you spring to pick it up. Or maybe you hold the door for someone behind you. Such acts of kindness to strangers were long thought to be unique to humans, but recent research on bonobos suggests our species is not as exceptional in this regard as we like to think.

Famously friendly apes from Africa's Congo Basin, bonobos will go out of their way to help strangers too, said Jingzhi Tan, a postdoctoral associate in evolutionary anthropology at Duke University.

A previous study by Tan and associate professor of Brian Hare found that bonobos share food with strangers. Now, in a new series of experiments, the team is trying to find out just how far this kindness goes.

The researchers studied wild-born bonobos at the Lola ya Bonobo sanctuary in the Democratic Republic of Congo.

In one experiment, they found that bonobos will help a stranger get food even when there is no immediate payback.

Sixteen bonobos were led one at a time into one of two adjacent rooms separated by a fence. The researchers hung a piece of apple from a rope just above the empty room, visible but out of reach.

The apes couldn't access the fruit or the rope. But if they climbed the fence they could reach a wooden pin holding the rope to the ceiling and release the dangling fruit, causing it to drop within reach of any that entered the next room.

A female bonobo embraces a newcomer on her first day in a new group. Credit: Lola ya Bonobo Sanctuary

The bonobos released the fruit roughly four times more often when an unfamiliar bonobo was in the adjacent room than when the room was empty.

What's more, the bonobos didn't wait to be asked for help, they just offered it. The researchers changed the size of the mesh surrounding the stranger's room so that in some trials they were able to stick their arms through the openings in the screen to beg for the treat, and in other trials they were not. The bonobos helped just as often whether the stranger gestured for help or not.

Bonobos' impulse to feel for strangers isn't entirely under conscious control, the researchers also found. In another experiment, they had 21 bonobos watch a series of short videos. In some videos, the apes saw a familiar group member either yawning or making a neutral expression. In other videos they watched complete strangers from the Columbus Zoo in the U.S. behaving the same way.

Just as watching another person yawn can make you yawn, yawning is contagious in bonobos too. Previous studies suggest the phenomenon is linked to a basic form of empathy called "emotional contagion," when one person's mood triggers similar emotions in others around them.

The researchers found that stranger yawns were just as contagious as those of groupmates.

The impulse to be nice to strangers is likely to evolve in species where the benefits of bonding with outsiders outweigh the costs, said Tan, now a postdoctoral scholar at the University California, San Diego.

Female bonobos leave the group where they were born to join a new group when they reach adulthood, where they form bonds with other unrelated adults they've never met. Bonobos, like humans, may simply be eager to make a good first impression.

"All relationships start between two strangers," Tan said. "You meet a , but you may meet them again, and this individual could become your future friend or ally. You want to be nice to someone who's going to be important for you."

Explore further: Bonobos will share with strangers before acquaintances

More information: Jingzhi Tan et al, Bonobos respond prosocially toward members of other groups, Scientific Reports (2017). DOI: 10.1038/s41598-017-15320-w

Related Stories

Why yawning is contagious in bonobos

November 14, 2012

Being socially close to another bonobo is more likely to make bonobo apes yawn in response to the other's yawns, according to research published November 14 in the open access journal PLOS ONE by Elisabetta Palagi and Elisa ...

Scientists complete Bonobo genome

June 13, 2012

In a project led by the Max Planck Institute for Evolutionary Anthropology in Leipzig, an international team of scientists has completed the sequencing and analysis of the genome of the last great ape, the bonobo. Bonobos, ...

Recommended for you

Some female termites can reproduce without males

September 24, 2018

Populations of the termite species Glyptotermes nakajimai can form successful, reproducing colonies in absence of males, according to a study published in the open access journal BMC Biology.

Photosynthesis discovery could help next-gen biotechnologies

September 24, 2018

Researchers from The University of Queensland (UQ) and the University of Münster (WWU) have purified and visualized the 'Cyclic Electron Flow' (CEF) supercomplex, a critical part of the photosynthetic machinery in all plants, ...

How fruits got their eye-catching colors

September 24, 2018

Red plums. Green melons. Purple figs. Ripe fruits come in an array of greens, yellows, oranges, browns, reds and purples. Scientists say they have new evidence that plants owe their rainbow of fruit colors to the different ...

Custom circuits for living cells

September 24, 2018

A team of Caltech researchers has developed a biological toolkit of proteins that can be assembled together in different ways, like Legos, to program new behaviors in cells. As a proof-of-concept, they designed and constructed ...

Birds' voiceboxes are odd ducks

September 24, 2018

Birds sing from the heart. While other four-limbed animals like mammals and reptiles make sounds with voiceboxes in their throats, birds' chirps originate in a unique vocal organ called the syrinx, located in their chests. ...


Adjust slider to filter visible comments by rank

Display comments: newest first

4 / 5 (1) Nov 07, 2017
More proof of my pet theory: Humans are the selfish, unruly, and destructive descendants of prehistoric primates. Due to bad behavior, our ancestors were outcast from the tree tops by their socially cohesive arboreal relatives. And just as many of us now look to up to the sky in supplication, so did our ancestors as they relied on the largess of their tree dwelling benefactors for food until the point at which they could adapt their diets to terrestrial food sources.

We are the mongrel result of a primate penal colony.

Yes, this just a fun joke. Don't blame me if you start seeing evidence for it in every primate study you see from now on.
2 / 5 (1) Nov 09, 2017
We are more likely descended from chimpanzees who are cannibalistic and primate eating carnivores. We out-evolved other hominids by killing them or eating them.
Mark Thomas
3 / 5 (1) Nov 09, 2017
There is a HUGE advantage of integrating into a successful group, but it comes at an evolutionary cost. For most of us that cost is being fundamentally altered such that we are predisposed to help the group and the individuals it contains, not only without being asked, but even without thinking about it. Apparently, the same evolutionary forces have been at work on the bonobos. Most of us have been so altered by the evolutionary process that it is abnormal to not feel good to help one another. These feelings go well beyond even our own species. Most of us feel good when we protect our pets and even wild animals and plants. I saw a video of divers removing an entangled fishing net that was slowly cutting into a whale's flesh and it was absolutely wonderful to see the whale freed from the net by divers who were actually risking their lives. We should embrace this part of our nature as real and necessary and even ennobling. It may be critical to facing the challenges ahead.
Mark Thomas
3 / 5 (2) Nov 09, 2017
The evolutionary effects of group living also neatly explain religion. Speaking about the religion I know best, Christianity, if you are within the group, you are nominally a brother or sister to be treated with kindness and respect. If you are outside the group, Christianity is flexible enough to allow you in if you are willing. If you challenge the group, you are going to be confronted by a united group who believes the group must be preserved at all costs. All cultures seem to have a religion of one sort or another, and you can see that flexible religion like Christianity is extremely useful for promoting interest of the group above others.
not rated yet Nov 10, 2017
'unrelated adults'. Unless these adults are from another planet, this isn't likely.
not rated yet Nov 10, 2017
Your article on bonobos refers to them as 'apes' awfully frequently, given how little your articles on humans do.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.